1. Field of Invention
This invention relates to qualitative and quantitative chemical analysis, and more particularly to processes, apparatus, media and signals for automatically identifying compounds in a sample.
2. Description of Related Art
The field of biometric identification has grown tremendously over the recent decade both from its relevance to medical diagnostics and to its application as a way to uniquely identify a person or an animal, for example. As diagnostic tools have become more sophisticated, complex liquid mixtures, such as human blood or urine for example, can now be analyzed to identify or search for particular compounds that can provide important diagnostic information to a medical technician or a doctor.
Generally, the separation and characterization of mixtures is fundamental to nearly every aspect of analytical chemistry and biochemistry. Most approaches to identify and quantify biological compounds in liquid mixtures require an initial compound separation (chromatographic or physical separation) step to separate a particular compound or set of compounds from the mixture. For example, gas chromatography, electrophoresis, and liquid chromatography are used to separate pure chemical components/compounds, for example, from a mixture before analysis is performed. Initial compound separation is required because most spectral identification processes, such as mass spectrometry or infrared, visible, and ultraviolet spectroscopy, require relatively pure samples in order to minimize noise and increase the accuracy of the measuring device. Spectral identification processes are expensive, manually intensive and require a great deal of technical expertise to be performed properly in an accurate, timely manner.
Nuclear magnetic resonance (NMR) has recently been shown to be an alternative approach to identify and quantify biological compounds without chromatographic separation. In this approach, radio frequency (RF) electromagnetic radiation is applied to a mixture of organic compounds to extract and measure a characteristic RF absorption spectrum of nuclei belonging to each specific organic compound. A large number of compounds are associated with well-defined peaks in the absorption spectrum and knowing which peaks are associated with certain compounds makes it possible to manually identify some of the compounds in the liquid mixture without resorting first to chromatographic separation. However, this process is still quite slow and requires a great deal of a priori information that relates each peak to a given compound. It can take a number of years for experts in NMR spectroscopy to acquire the knowledge required to analyze NMR spectra to accurately identify and quantify compounds in sample mixtures.
Therefore what is desired is a process and apparatus for quickly, accurately and automatically identifying a number of compounds which may be present in complex liquid mixtures without involving chromatographic separation and without requiring people who are experts in NMR techniques.